Among prior art compounds which inhibit a Na.sup.+ /Ca.sup.2+ exchange system selectively and prevent overload of Ca.sup.2+ in cells regarded as important in the cell injury mechanism after ischemia or reperfusion, there are known compounds having a quinazoline skeleton as described in Japanese Patent Kokai 7-41465. However, there is no report that the compounds having a phenoxyaniline skeleton as shown in the present invention have an inhibitory action on a Na.sup.+ /Ca.sup.2+ exchange system.